When electroplating sheet material, and specifically galvanizing thin sheet steel, one conventional plating arrangement utilizes a tank containing a bath of plating solution, and several large-diameter rolls are supported on the tank so that lower portions of the rolls are immersed in the tank. The sheet material is engaged with and wrapped around the lower portions of the rolls so as to progressively move through the electroplating bath in response to roll rotation. The roll is provided with a current-conducting member extending generally around the periphery thereof for contact with the sheet material so that this member and the sheet effectively function as a cathode, and the lower periphery of the roll as immersed in the bath is also disposed closely adjacent but slightly spaced from an arcuate anode which is fixed relative to the tank, whereby the sheet material passes closely adjacent the anode as it is wrapped around the lower portion of the roll. Electrical current of high amperage is applied to a shaft which is fixed to and rotates with the roll, and for this purpose it is conventional to provide a current collector which is mounted on the shaft exteriorly of but adjacent the tank. This current collector, which has been in use on electroplating apparatus for many years, includes a collector rotor which is secured to a tapered end of the roll shaft which projects outwardly from the tank, and this collector rotor is surrounded by an enlarged and substantially hollow stationary housing. This housing mounts therein an extremely large number (for example 60) of conventional current-transfer brushes or contacts which are disposed in slidable contact with the rotating rotor. These brushes are individually coupled to current-transfer cables which project to an exterior source of direct current. The anode associated with the rotor is also coupled to the source of direct current. With this known arrangement, which has been conventionally industrially used for many years, the electrical potential from the roll cathode and the radially adjacent anode coact with the electrolytic solution in a conventional manner to permit deposit of plating material on the sheet material. While this known apparatus and technique have been utilized for many years, the supply of high amperage current to the rotatable roll has long presented a significant problem due to the hostile and corrosive environment created by the electrolytic solution in the tank, and the high amperage required to successfully perform the process. Due to the rotation of the roll relative to the tank, the conventional current collector used for transferring electric current to the roll shaft have presented an ongoing maintenance problem both due to wear and due to deterioration caused by the corrosive environment. Maintaining, replacing and/or rebuilding the current collector has thus been a common occurrence which has created an excessive amount of undesirable maintenance and an excessively undesirable amount of shut down time of the apparatus. More specifically, this conventional current collector inherently results in excessive brush wear and, due to the voltage which is necessarily required by the electroplating operation, results in an undesirable amount of power loss (i.e., voltage drop). The high current and the inefficient current transfer associated with the large number of current-conducting brushes also result in excessive heat generation, and this can be combatted only by flooding the interior of the housing in surrounding relationship to the brushes with water. This known and long utilized current collector has exhibited less than desirable performance characteristics, but has nevertheless been continually used due to lack of a better alternative.
In another conventional plating arrangement, there is again provided a tank containing a bath of plating solution, and having several large-diameter rolls supported thereon so that the rolls are immersed in the solution. In this arrangement, however, there are provided vertically-opposed pairs of rollers disposed in generally horizontally aligned relationship, with the vertically opposed pairs defining a nip therebetween which is disposed in the plating bath. The sheet material is then fed generally horizontally into the nip of one pair of rollers, and then fed tautly generally horizontally through the bath to the nip associated with the next pair of rollers. Electrical potential is supplied to the rollers which, due to their contact with the sheet material, effectively function as a cathode. An anode formed as a generally horizontally enlarged plate is stationarily positioned in the bath so as to extend generally between adjacent lower rolls in close proximity to the sheet which extends tautly between the nips of adjacent roll pair. With this arrangement, current collector devices are again coupled to the shafts of the rolls for transmitting electrical energy thereto, which current collectors may again be of the type described above, or in the alternative may be of the type employing a plurality of cables which wrap around the roll shaft to permit current transfer thereto. This latter type of current collector also possesses obvious disadvantages in that it is inefficient and results in undesirable voltage drop or loss.
It is thus an object of this invention to provide an improved current collector for permitting transfer of high amperage current to the shaft of a rotatable electroplating roll, which arrangement is believed to provide significantly improved performance and thus overcome many of the known problems associated with prior electroplating systems.
More specifically, this invention relates to an electroplating apparatus, namely an apparatus having a tank containing a bath of an electrolytic solution, and a roll supported for immersion into the electrolytic bath for transporting a sheet material through the bath, with the roll having a current collector rotatably supported on a shaft thereof for transmitting high amperage electricity to the roll. The improved current collector of this invention is supported on a part of the roll shaft which projects exteriorly of the tank side wall. The current collector incorporates a sleeve-like housing structure which surrounds and is rotatable relative to the shaft and mounts therein a small number of conductive shoes which are of a highly electrically conductive material and are spring urged for snug radial contact with a conductive ring secured to a conductive sleeve arrangement which snugly axially and nonrotatably mounts to the roll shaft.
In the improved arrangement of this invention, as aforesaid, the nonrotatable housing of the current collector cooperates with the sleeve arrangement to define a generally sealed interior annular chamber in which the current-conducting shoes are positioned. A closed-loop pressurized lubricant system is connected to the current collector for permitting a substantially continuous supply of lubricant into the chamber and withdrawal of lubricant therefrom to provide for both substantial lubrication and cooling to permit transmission of high amperage electric current through the shoes to the conductive ring and thence therethrough to the shaft. This arrangement isolates the critical relatively-rotatable current transferring contact surfaces from the hostile environment and additionally provides for proper lubrication and cooling thereof to achieve relatively long and maintenance free operation. This arrangement also greatly reduces power loss (i.e., voltage drop) to provide significantly more efficient transfer of electrical potential to the roll.
Other objects and purposes of the present invention will be apparent to persons familiar with arrangements of this general type upon reading the following specification and inspecting the accompanying drawings.